Carbonless copy forms are well known. A typical two-part form includes a top sheet having a coated back (CB) containing microencapsulated (generally colorless) dye, and a bottom sheet having a coated front (CF) containing a reactive dye-revealing substance. The top and bottom sheets are assembled, such as by gluing, into a "manifold", or many part set. The pressure of writing on the front surface of the top sheet causes the encapsulated dye on the CB-coated back surface of the top sheet to rupture, releasing dye onto the CF-coated front surface of the bottom sheet, whereupon the writing is revealed in a contrasting (visible) color on the front surface of the bottom sheet.
Multiple carbonless copies are produced in a similar manner. One or more intermediate sheets are assembled between the top and bottom sheets. Each intermediate sheet has a carbonless front (CF) coating on its front surface for revealing the dye from the previous sheet, and has a carbonless back (CB) coating on its back surface for releasing dye to the next sheet in the set.
With these techniques, one or more carbonless copies of information entered on the front surface of the original (top) sheet can be reproduced on a surface of the copy (intermediate and bottom) sheets.
The chemistry of the CB and CF coatings is well known, as are techniques for applying these coatings to paper stock.
A variation of the above is found in so-called "two-way write" systems. One such example is found in U.S. Pat. No. 4,000,916, issued to Lucas, which describes a manifold report form having three superimposed record sheets (top, middle and bottom). Carbon sheets and protective sheets are arranged between the record sheets. Information entered on the front surface of the top record sheet is reproduced on the front surfaces of the middle and bottom sheets. The form is then flipped over, in its entirety, and various carbon and protective sheets are removed. Information entered on the back surface of the bottom sheet is reproduced on the back surface of the middle and top sheets.
With such two-way write systems, a true original is not formed. Rather, each of the top and bottom sheets contains "original" (e.g., hand written) information on only one surface, and "copy" (reproduced by carbon paper or the CB/CF dye reaction) information on the other surface. Such a bifurcation of the original information is unsuitable in many applications, such as for legal forms.
U.S. Pat. Nos. 4,715,620 and 4,762,342, issued to Thompson, attempt to solve the challenge of providing a "true" original where the top sheet has "original" information on the front and back surfaces thereof. Therein, top, intermediate and bottom sheets are assembled into a manifold having a stub. Patterned carbon papers and/or carbonless coatings are employed, between the various sheets, as in the two-way write systems. Information is entered on the front surface of the top sheet. The top sheet is then folded around the stub so that its front surface is in contact with the back surface of the bottom sheet. Additional information is then entered on the exposed back surface of the top sheet. The front surface of the top sheet is coated with carbonless CB and the back surface of the bottom sheet is coated with carbonless CF so that the information entered on the back surface of the top sheet is reproduced on the back surface of the bottom sheet.
The problems with Thompson's techniques include the following: 1) It is extremely difficult to maintain registration (alignment) of the top sheet when it is folded around the stub. Hence, it is suggested by Thompson that the stub be gently folded over along with the top sheet. This causes a gap between the top sheet and bottom sheet, which is in apposite to carbonless image forming. The top sheet, when folded over the stub in this manner, must be smoothed out prior to entering the additional information on the back surface of the top sheet. Additionally, if the stub is not folded properly, the top sheet will not be in register with the other sheets when it is flipped over for entering information on the back surface thereof. 2) The carbonless CB coating on the front surface of the top sheet is difficult to write upon. For instance, the tip of a ball point pen will tend to become clogged by dye released from the microcapsules in short order.
The implementation of all of the above-described manifold forms is further complicated by the need for machinery necessary to collate, glue and/or staple individual, dissimilarly coated sheets of paper, carbon papers and protective sheets into a manifold arrangement. This necessitates costly set up charges for the equipment, creates delays in going from paper stock to preprinted form, and creates cumbersome inventory requirements.